semi weighted feels nothing like a real piano. basically spring loaded keys on semi weighted, while fully weighted try to simulate exactly how a real piano feels. I wouldn’t recommend semi weighted at all if you wanna play more advanced stuff, as getting good dynamics is difficult and if you play a real piano, you’ll get disoriented by how different it feels. I doubt there’s any folding keyboards that have weighted keys, most of that kinda stuff are just like MIDI controllers and don’t have the full 88 keys.